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TitleInvestigations of nuclear decay half-lives relevant to nuclear astrophysics
TagsNuclear Physics
LanguageEnglish
File Size1.4 MB
Total Pages129
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Page 65

4.3 The outlines and instrumentation of the experiment 55

Figure 4.1: (left) The dilution refrigerator at the Atomki Cryophysics Laboratory.
(right) The γ detector watching the cooled sample through the thin exit windows
(see also Fig. 4.2).

thus the samples were similar, too. This time the sample holder was placed

at a (6.5 – 7.5) cm distance from the tantalum boat into which (38 – 61) mg

99.9999 % purified germanium nuggets were placed. For backing we used

50µm thick high purity aluminum foils. Both the germanium and Al back-

ings were manufactured by Advent Research Materials. Four targets were

prepared altogether.

Three of the produced targets were activated, one in each measurement

runs. For the activation the chamber described in Section 5.3 was utilized.

This time the protons provided by the cyclotron had an energy of Ep =

10.4 MeV. The intensity of the beam was (2.4 – 5)µA. The irradiations took

(6.5 – 23) h. A summary of the irradiation runs can be seen in Table 4.3.

4.3.3 γ detection

The γ measurement was performed in the Cryophysics Lab while the sample

was decaying inside the refrigerator. The applicable measuring geometry

was constrained by the cooling system. The γ rays created by the de-

excitation of the daughter nuclei of 74As could escape the chamber of the

sample holder through three thin aluminum windows. The 40 % relative

efficiency HPGe detector described in Section 3.6 was used to detect the γ

activity of the samples. The γ detector was placed directly in front of the

outmost window, the diameter of which was approximately the same as the

diameter of the detector (7.9 cm). The distance between the source and the

Page 129

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